Natural gas may be the cleanest fossil fuel, but it can be an unnecessary pest when it’s produced as waste from remote offshore oil wells. Brazilian state oil company Petrobras is fueling a race between two developers of modular chemical reactors that could turn this “associated gas” into synthetic crude.
U.K.-based Compact GTL will unveil a commercial partnership today with Sumitomo Precision Products, a Japanese industrial company with which Compact GTL is building a gas-to-liquid (GTL) pilot plant to be delivered to Petrobras by this summer. Nipping at Compact GTL’s heels, meanwhile, is Columbus-based microreactor developer Velocys, which announced plans last month to build a pilot plant for Petrobras using its potentially more compact design.
Success by either company could slash greenhouse gas emissions generated when remote natural gas is simply burned off at oil wells (this accounts for 0.5% of all carbon dioxide emissions from fossil fuels, according to a 2005 estimate by Oak Ridge National Laboratory). “Today we flare enough natural gas to power Germany,” says Jeff McDaniel, business development director for Velocys.
Petrobras has a particularly stringent need for a solution to this wasted natural gas. It’s now developing its Tupi field, 300 kilometers offshore, which will be the world’s largest deepwater oil field, according to energy and mining consultancy Wood Mackenzie. “One of their big challenges is going to be how to deal with the associated gas,” says Ruaraidh Montgomery, a Houston-based Wood Mackenzie analyst for Latin America.
Both Compact GTL and Velocys use the same catalytic reactions found in massive GTL facilities: natural gas is first mixed with steam to produce carbon monoxide and hydrogen; the resulting syngas is then converted into a waxy form of synthetic crude oil.
However, this is commercially viable only on a huge scale, such as the 140,000-barrel-per-day plant that Shell is building in Qatar, which will use two dozen 1,200-ton reactor vessels. Velocys and Compact GTL must squeeze the same chemistry into a package that will fit on an offshore platform or on the deck of the floating production, storage, and offloading (FPSO) vessels increasingly used to explore and service offshore oil fields.
What makes this possible is performing the chemical reactions in microchannels between one and five millimeters wide, and at higher temperatures and pressures. Rapid heat transfer enables more precise control of the temperature, and this lessens the risk of runaway reactions that could damage the catalysts or, in a worst-case scenario, destroy the plant.
The result, according to Velocys, is a roughly 200-fold acceleration of the steam “reforming” of methane into syngas. “The contact time [for reactants] in a conventional steam reformer is around one second. In microchannels, it’s around five milliseconds,” says McDaniel. The microchannel synthetic crude step is about 10 to 15 times faster. Overall, that should shrink the volume of equipment needed for an integrated GTL plant about tenfold.